This invention relates generally to a fluid activated percussive impact tool having a piston reciprocal in a housing of such tool, and more particularly to a jackhammer in which the piston is longitudinally reciprocal and the drill steel is rotated as well as impacted by the piston.
Typical jackhammer construction uses a piston which is reciprocated by a fluid cycle to provide percussive energy to a drilling steel. Proper operation of the drill requires that the drill steel rotate as the piston reciprocates. This rotary motion is accomplished through a series of splines and a clutching mechanism. The spline geometry is normally such that the piston is required to rotate with the drill steel. A typical drill will operate on a two inch stroke at 2000 blows per minute which is approximately 670 ft/min surface feet in the axial direction. The drill typically rotates at 140-150 rpm. An average piston diameter is 2 inch which results in a rotary surface footage of approximately 75 ft/min. Both components of surface footage contribute to the total wear of the piston geometry to its surrounding components. Elimination of the rotary component of surface footage would reduce the wear between these components. Consequently, performance and part integrity should increase as the drill is operated.
For rotating the drill steel, a typical configuration uses a splined nut in a jackhammer. The splined nut has threaded outside diameter with an internal spline type of geometry. The threaded area is usually grounded to another component within the drill such as a chuck or chuck driver. The internal splines on the nut engage with splines on the piston. The torsional interaction between the splines of the piston and nut often results in high wear of the nut itself. Repair of the assembly is difficult and requires special wrenches to disassemble the nut from the piston or chuck geometry.
The foregoing illustrates limitations known to exist in present jackhammers. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.